Drilling fluid



United States Patent Office 3,505,219 Patented Apr. 7, 1970 U.S. Cl.252-85 Claims ABSTRACT OF THE DISCLOSURE An aqueous drilling fluiddispersant and a method of drilling wells using said drilling fluidwhich contains a substitutedcycloalkane drilling fluid dispersant,namely 1,2,3,4,5,6 hexahydroxycyclohexane, 1,3,4,Stetrahydroxycyclohexanecarboxylic acid or1,2,3,4-cyclopentanetetracarboxylic acid.

This invention relates to a novel aqueous drilling fluid for drillingwells through sub-surface formations by means of well drilling tools,and particularly to such an aqueous well drilling fluid having improveddispersibility as a result of containing therein a novel dispersant ashereinafter more fully described. The invention is also concerned with amethod of drilling wells employing the novel aqueous drilling fluid.

Drilling fluids, or muds as they are sometimes called, are slurries ofclayey solids used in the drilling of wells for tapping undergroundcollections of oil, gas, brine or Water. Such fluids have a number ofdifferent functions, the most important of which are to assist in theremoval of cuttings from the well, to seal off formations of gas, oil orwater which may be encountered at different levels, to lubricate thedrilling tool and drill pipe which carries the tool, and to hold thecuttings in suspension in event of shut-downs in drilling.

An ideal drilling fluid is a thixotropic colloidal system, i.e., a fluidwhich on agitation or circulation (as by pumping or otherwise), has ameasurable relatively low viscosity and is free flowing (not plastic),particularly at high temperatures; but when such agitation 0rcirculation is halted, the fluid sets or gels. The rate of gel formationis such as to permit the cuttings to fall only a short distance beforethe gel structure is sufliciently strong to support them.

When such a drilling fluid having the proper viscosity, the propergelrate and proper gel strength is circulated through a' well bore, it hasa sufliciently high viscosity to carry the cuttings and sand from thebottom of the hole to the surface and it has a gel rate such as to allowthe cuttings and sand to settle in a settling pit. On standing in aquiescent state, it develops su tficient gel strength to prevent thesettling of the cuttings, sand or weighting material, etc., in the wellbore when it becomes necessary to discontinue circulation for anyappreciable period of time. Such afluid is also characterized by itsability to form a mud cake on the borehole wall, thereby assisting insealing off the traversed formations and inhibiting socalled Water loss,i.e., loss of Water from the drilling fluid.

One of the principal problems in mud chemistry is the production ofsuitable drilling fluids having satisfactory dispersibility, and thenecessary thixotropic properties discussed above.

In accordance with the present invention the problems of dispersibilityin aqueous drilling fluids can be solved by incorporating in an aqueousdrilling fluid as the dispersant a substituted cyeloalkane selected fromthe group consisting of 1,2,3,4,5,6-hexahydroxyclohexane, 1,3,4,5tetrahydroxycyclohexanecarboxylic acid and1,2,3,4-cyclopentanetetracarboxylic acid.

It is known from the article appearing in Zhur. Priklad. Khem. 35, pages638-647 (1962), Organic Viscosity Reducers in Clay Solutions by D.Tischenko and S. Fleisher (CA, 57, 2491g, 1962), that theortho-dihydroxybenzenesulfonic acids, theortho-dihydroxy-alpha-toluenesulfonic acids and Water soluble saltsthereof are viscosity reducing agents in clay laden drilling fluidswhereas the corresponding metaand para-dihydroxybenzenes including thecorresponding sulfonic acid. derivatives and water soluble salts thereofare ineffective viscosity reducing agents for aqueous drilling fluids.

The term substituted cycloalkane as used in the specification and claimsis intended to cover the following cycloalkanes: 1,2,3,4,5,6hexahydroxycyclohexane, 1,3, 4,5 tetrahydroxycyclohexane-carboxylic acidand 1,2,3, 4-cyclopentanetetracanboxylic acid.

The substituted cycloalkanes of the present invention may be added to anaqueous drilling fiuid in amounts ranging from about 0.1 pound to about10 pounds per barrel of drilling fluid. In general, it has been foundthat amounts less than 0.1 pound per barrel do not produce completelysatisfactory results in terms of dispersing activity whereas amountsabove about 10 pounds per barrel are economically unattractive and noimproved results are obtained therewith. A preferred range for thesubstituted cycloalkanes of the present invention is from about 0.25 toabout 7 pounds per barrel of drilling fluid for most consistent resultsand efficiency.

In the tables, gel strength (Gels) is reported as determined by ashearometer in accordance with the procedure in the American PetroleumInstitute publication RP-29, results being expressed either as pounds/square feet or as time in seconds for a tube to settle in the mud (afterthe mud has stood for zero time and for 10 minutes). If it settles inmore than 60 seconds, shear is reported as pounds per hundred squarefeet. Yield Point (YP) is calculated by subtracting the PlasticViscosity (PV) from the Fann Viscosity reading at 300 r.p.m. PlasticViscosity (PV) is obtained by calculation, subtracting the Fann readingat 300 r.p.m. from the 600 r.p.m. reading. Apparent Viscosity (AV) isequal to one half of the Fann Viscosity reading obtained at 600 r.p.m.The fluidity of a mud can be back calculated from these data, theresults being expressed in Fann Viscosity at 600 r.p.m. and 300 r.p.m.for a direct reading viscosimeter.

The properties of the base muds are sown in the table.

The test data set forth in the following table indicate the surprisingadvantages of the subsituted cycloalkanes of the present invention anddemonstrate the beneficial results of same in improving thedispersibility of drilling fluids.

Representative physical proprties of drilling fluids both before andafter addition of the substituted cycloalkanes of the present inventionare shown in the table. In each example the amount of material ormaterials added to the base mud, if any, is shown, expressed in terms ofpounds of material per barrel of drilling fluid.

TABLE Shearometer Gels, lb./100 Additional Amount 11;." API Additive,and Type Ap. Vls., Pm, W.L., PF, Ca, Time, Ex. lbs. TypeMud DispersantPV cpe. 10 1 pH cc. cc. cc. p.p.m. hours 1.0 A 24 9 28. 6 0 3.8 11. 0 16(1) LpH 2.0 19 7 22.5 0 0 9.6 16 7. 0 19 21. 5 0 l 0 5 11. 1 16 9 10 149. 4 0. 25 (2) LpH 0. 5 Bf 14 11 19. 5 0 I 4.8 9. 5 2 10 9. 4 16 8 4 l09. 3 25 (2a) 2.0 B 11 9 15. 5 0 3 3. 7 9. s 2 16 7 19. 5 9. 6 16 (3) LpH0.5 CI 14 7 17.6 0 0 l1 9.3 16 2. 0 14 4 16 0 0 ll 9. 4 16 (4)....2.51ime MOD SC 2.5 C 10 4 8 0 1 0 11. 7 5. 1 16 I LpH-Low pH mud. MODSC-Modified shale control mud;

* A1,2,3,4,5,6-hexahydroxycyclohexane.

rB1,3,4,5tetrahydroxycyclohexanecarboxylic acid.

IC1,2,3,4-cyclopentanetetracarboxylie acid.

The table above shows that the substituted cycloalkanes of the presentinvention are effective dispersants in low pH and modified shale controldrilling fluids at concentrations of from 0.5 to 7.0 pounds per barrel.

A modified shale control drilling fluid contains lime and caustic but isfree from an added water soluble calcium salt. A modified shale controldrilling fluid containing lime, caustic, if needed, and the noveldispersants of the present invention will provide the same beneficialresults as achieved with the shale control drilling fluid of Weiss andHall, US. 2,802,783, i.e. stabilizing and hardening the shale formationsin contact therewith. This surprising result is accomplished in theabsence of the added water soluble calcium salt required by the Weissand Hall patent to attain the necessary shale control chemistry need tostabilize and harden the shale formations in contact therewith.

I claim: 1

1. An aqueous drilling fluid containing clayey solids and as thedispersant at least about 0.1 pound per barrel of drilling fluid of asubstituted cycloalkane selected from the group consisting of1,2,3,4,5,6-hexahydroxycyclohexane, 1,3,4,5tctrahydroxycyclohexanecarboxylic acid and1,2,3.,4-cyclopentanetetracarboxylic acid.

2. An aqueous drilling fluid as claimed in claim 1 wherein thesubstituted cycloalkane is l,2,3,4,5,6-hexahydroxycyclohexane.

3. An aqueous drilling fluid as claimed in claim 1 wherein thesubstituted cycloalkane is 1,3,4,5 tetrahydroxycyclohexanecarboxylicacid.

4. An aqueous drilling fluid as claimed in claim 1 wherein thesubstituted cycloalkane is 1,2,3,4-cyclopentanetetracarboxylic acid.

5. An aqueous drilling fluid as claimed in claim 1 wherein thesubstituted cycloalkane is present in the drilling fluid in an amount offrom about 0.1 to about 10 pounds per barrel of drilling fluid.

6. An aqueous drilling fluid as claimed in claim 1 wherein thesubstituted cycloalkane is present in the drilling fluid in an amount offrom about 0.25 to about 7 pounds per barrel of drilling fluid.

7. In a method of drilling wells wherein a drilling fluid is passedthrough the well in contact with earth formations during the drillingoperation, the improvement which comprises contacting said earthformations with an aqueous drilling fluid containing clayey solids andas the dispersant at least 0.1 pound per barrel of drilling fluid of asubstituted cycloalkane selected from the group consisting of1,2,3,4,5,6 hexahydroxycyclohexane, 1,3,4,5-tetrahydroxycyclohexanecarboxylic acid and1,2,3,4-cyclopentanetetracarboxylic acid.

8. A method as claimed in claim 7 wherein the substituted cycloalkane isl,2,3,4,5,@hexahydroxycyclohexane.

9. A method as claimed in claim 7 wherein the substituted cycloalkane isl,3,4,5 tetrahydroxycyclohexanecarboxylic acid.

10. A method as claimed in claim 7 wherein the substituted cycloalkaneis 1,2,3,4 cyclopentanetetracarboxylic acid.

References Cited UNITED STATES PATENTS 1,819,646 8/ 1931 Loomis et a12528.5 X 2,112,553 3/1938 Bartow et a1 260-631 2,393,273 1/1946 Wayne2528.5 2,545,169 3/1951 Salathiel 2528.5

HERBERT B. GUYNN, Primary Examiner U.S. Cl. X.R.

